Valvular heart disease: shifting the focus to the myocardium

Adverse cardiac remodelling is the main determinant of patient prognosis in degenerative valvular heart disease (VHD). However, to give an indication for valvular intervention, current guidelines include parameters of cardiac chamber dilatation or function which are subject to variability, do not directly reflect myocardial structural changes, and, more importantly, seem to be not sensitive enough in depicting early signs of myocardial dysfunction before irreversible myocardial damage has occurred. To avoid irreversible myocardial dysfunction, novel biomarkers are advocated to help refining indications for intervention and risk stratification. Advanced echocardiographic modalities, including strain analysis, and magnetic resonance imaging have shown to be promising in providing new tools to depict the important switch from adaptive to maladaptive myocardial changes in response to severe VHD. This review, therefore, summarizes the current available evidence on the role of these new imaging biomarkers in degenerative VHD, aiming at shifting the clinical perspective from a valve-centred to a myocardium-focused approach for patient management and therapeutic decision-making. In the presence of severe valvular heart disease (and associated comorbidities), cardiac chambers are exposed to either pressure (as in aortic stenosis) or volume overload (as in mitral regurgitation), which triggers at first a series of adaptive mechanisms to release wall tension and maintain cardiac output (namely chamber hypertrophy and/or dilatation). However, these compensatory phenomena are soon followed by maladaptive myocardial changes such as reactive fibrosis, microvascular ischemia and cell death with replacement fibrosis, which substantially impair their function. New imaging biomarkers (namely obtained from echocardiography and cardiac magnetic resonance imaging) are capable of depicting the occurrence of such maladaptive changes with important potential impact on patient risk stratification and decision making. Particularly, global longitudinal strain has shown to be a sensitive marker of systolic dysfunction and cardiac magnetic resonance imaging has the key strength of myocardial tissue characterization, including fibrosis an inflammation, but also myocardial perfusion and energetics, and therefore offers an in-vivo “virtual histology”.